As radio access technology (RAT) of the fifth generation (5G) mobile communication systems following Long Term Evolution (LTE)/LTE-A (Advanced), non-orthogonal multiple access is being focused on. In Orthogonal Frequency-Division Multiple Access (OFDMA) and Single-Carrier Frequency-Division Multiple Access (SC-FDMA) used in LTE, radio resources (for example, resource blocks) are allocated to users in a non-overlapping manner. Such schemes may be referred to as orthogonal multiple access. On the other hand, in non-orthogonal multiple access, radio resources are allocated to users in an overlapping manner. In non-orthogonal multiple access, signals of users interfere with one another, but a signal for each user is extracted by a high-precision decoding process on a reception side. Theoretically, non-orthogonal multiple access can implement a higher cell communication capacity than orthogonal multiple access.
As one of radio access technologies classified as non-orthogonal multiple access, superposition coding (SPC) multiplexing/multiple access is exemplified. SPC is a technique in which signals to which different power is allocated are multiplexed using radio resources of at least partially overlapping frequency and time. On the reception side, in order to receive or decode signals multiplexed using the same radio resources, interference cancellation and/or repeated detection are performed.
As examples of SPC or techniques equivalent to SPC, Patent Literatures 1 and 2 disclose techniques of setting an amplitude (or power) that enables appropriate demodulation and decoding. In addition, for example, Patent Literature 3 discloses a technique of enhancing successive interference cancellation (SIC) for receiving a multiplexed signal.